A number of lines in the robustly applauded speech delivered by Melania Trump at the Republican national convention on Monday night appear to have been lifted verbatim from a speech Michelle Obama delivered at the 2008 Democratic convention.

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“Barack and I were raised with so many of the same values, that you work hard for what you want in life, that your word is your bond and you do what you say you’re going to do,” Obama told the gathering of Democrats in 2008.

“And Barack and I set out to build lives guided by these values, and pass them on to the next generation. Because we want our children – and all children in this nation – to know that the only limit to the height of your achievements is the reach of your dreams and your willingness to work for them.”

Trump told GOP delegates on Monday: “From a young age, my parents impressed on me the values that you work hard for what you want in life, that your word is your bond and you do what you say and keep your promise.

“That you treat people with respect. They taught and showed me values and morals in their daily life. That is a lesson that I continue to pass along to our son, and we need to pass those lessons on to the many generations to follow, because we want our children in this nation to know that the only limit to your achievements is the strength of your dreams and your willingness to work for them.”

On Tuesday morning, Trump campaign chairman Paul Manafort said it was “just absurd” to claim that Melania Trump had plagiarised the first lady.

“There’s no cribbing of Michelle Obama’s speech,” Manafort told CNN, adding “there’s no feeling on her part that she did it.” Manafort suggested that she was simply using “words that are common words”.

In an initial statement issued at 2am, Jason Miller, the campaign’s senior communications adviser and Trump’s speechwriter, had said Melania Trump’s speech included “fragments” of others’ speeches that “reflected her own thinking”, though did not directly answer accusations of plagiarism.

Miller added that the speech was produced by Melania Trump’s “team”. This runs counter to her own statements in an interview with NBC prior to the speech, in which she claimed to have written the speech herself.

A campaign source suggested to the Guardian that the blame lay with Rick Gates, a longtime aide to top Trump strategist Paul Manafort. The source said Gates signed off on the speech and edited it.

Manafort took advantage of his decades of experience as well as the fact that he refused to accept a salary from Trump as he moved into the presumptive nominee’s orbit. A veteran of campaigns going back to Gerald Ford’s 1976 re-election effort, Manafort moved to hire longtime advisers and associates such as Gates.

Jon Favreau, a White House speechwriter for the Obama administration, pointed out that Michelle Obama’s writer used to work for Hillary Clinton:

Jon Favreau (@jonfavs)

Sarah Hurwitz, Michelle's head speechwriter, used to be Hillary's. So the Trump campaign plagiarized from a Hillary speechwriter.

Plagarism scandals have periodically haunted American politics. Infamously, the 1988 presidential campaign of the current vice-president, Joe Biden, was ended over allegations that the then senator from Delaware had plagiaried Neil Kinnock, the leader of the British Labour party at the time.

In an interview with Matt Lauer of NBC, Melania Trump said of her speech: “I wrote it with a little help as possible.”